Semiconductor light-emitting devices including light emitting diodes (LEDs), resonant cavity light emitting diodes (RCLEDs), vertical cavity laser diodes (VCSELs), and edge emitting lasers are among the most efficient light sources currently available. Materials systems currently of interest in the manufacture of high-brightness light emitting devices capable of operation across the visible spectrum include Group III-V semiconductors, particularly binary, ternary, and quaternary alloys of gallium, aluminum, indium, and nitrogen, also referred to as III-nitride materials. Typically, III-nitride light emitting devices are fabricated by epitaxially growing a stack of semiconductor layers of different compositions and dopant concentrations on a sapphire, silicon carbide, III-nitride, or other suitable substrate by metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or other epitaxial techniques. The stack often includes one or more n-type layers doped with, for example, Si, formed over the substrate, one or more light emitting layers in an active region formed over the n-type layer or layers, and one or more p-type layers doped with, for example, Mg, formed over the active region. Electrical contacts are formed on the n- and p-type regions.
In commercial III-nitride LEDs, the semiconductor structure is typically grown by MOCVD. The nitrogen source used during MOCVD is typically ammonia. When ammonia dissociates, hydrogen is produced. The hydrogen forms a complex with magnesium, which is used as the p-type dopant during growth of p-type materials. The hydrogen complex deactivates the p-type character of the magnesium, effectively reducing the dopant concentration of the p-type material, which reduces the efficiency of the device. After growth of the p-type material, the structure is annealed in order to break the hydrogen-magnesium complex by driving off the hydrogen.